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Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
PowerNex Associates Inc.
Module #1
Basic Electricity
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Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Module 1
Learning Objectives
To gain an understanding of the following:


Basic Electricity (1A)
 Units of Measurement
 Energy and Power
 Ohm’s Law and Joule’s Law
 Electrical Losses, Parallel Paths
 AC and DC
 Frequency
 The Transformer
 Real and Reactive Power
 Power Factor
 Three Phase Power
Geography and History related to the Ontario power system (1B)
 History and Growth of Ontario’s Power System
 Functions performed by Ontario Hydro and where they now belong
 The world outside Ontario, the interconnected system
 NERC/NPCC
Slide 2
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Module 1A
Basic Electricity
Units of measurement
Voltage (volts)
Current (amps)
Resistance (ohms)
Frequency (hertz)
Power (watts)
Reactive Power
Apparent Power
v (Kv)
I or A
Hz
w (Mw)
var (Mvar)
va (Mva)
Slide 3
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Basic Electricity
Units of measurement
Kilo (K)
Mega (M)
Giga (G)
Tera (T)
1,000
1,000,000
1,000,000,000
1,000,000,000,000
Typically
Volts in Kv
Watts in Mw
Current as is
eg 230 Kv
eg 500 Mw
eg 100 A
Slide 4
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Basic Electricity
Energy and Power
Slide 5
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Basic Electricity
 Energy is the ability or capacity to do work.
 Energy and work are measured in the same units: eg joules. There are
two main types of energy viz;
 Potential energy (stored energy, eg gravity, coal, oil, gas, the atom).
 Kinetic energy (motion energy, eg electrical energy, wind, sound)
 Energy can be neither created nor destroyed (law of conservation of
matter and energy), but it can be changed from one form into another
 From potential energy to mechanical energy to electrical energy (as
is the case with a hydro electric facility)
 From heat energy in coal to mechanical energy to electrical energy
(as is the case of a fossil fired facility)
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Basic Electricity
Energy and Power


The basic energy unit is the Btu. This stands for British thermal
unit. A Btu is defined as the amount of heat energy it takes to raise
the temperature of one pound of water by one degree Fahrenheit,
at sea level.
One Btu roughly equals:
 An average candy bar
 One match

It takes, for example, about 2,000 Btus to make a pot of coffee.

1,056 joules = 1 Btu

In most countries (except for the USA) energy is measured in
joules rather than Btus.
Slide 7
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Energy and Power
BTU Content of Common Energy Units
 1 gallon (imp) of gasoline = 149,000 Btu
 1 litre of gasoline = 33,000 Btu
 1 gallon (imp) of diesel fuel = 167,000 Btu
 1 litre of diesel fuel = 37,000 Btu
 1 barrel(42 US gallons/ 34 imp gallons) of crude oil = 5,800,000 Btu
 1 cubic foot of natural gas = 1,031 Btu
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Basic Electricity
Energy and Power
 Power is a measure of how much work can be performed in
a given amount of time or how rapidly a standard amount of
work is done.
 American cars for example are rated in "horsepower". In
Europe many cars are rated in Kw. (1 horsepower = 0.746
Kw)
 The power of a car's engine won't indicate how high a hill it
can climb or how much weight it can tow, but it will indicate
how fast it can climb a specific hill or tow a specific weight
Slide 9
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Basic Electricity
Energy and Power
Slide 10
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Basic Electricity
Energy and Power
Slide 11
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Basic Electricity
Energy and Power
Slide 12
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Basic Electricity
Energy and Power
Slide 13
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Basic Electricity
Ohm’s Law and Joule’s law
Slide 14
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Basic Electricity
Ohm’s Law and Joule’s law
Water analogy for Voltage, Current and Resistance
 Voltage (V)equivalent to
water pressure
 Current (I) equivalent to
water flow
 Resistance (R) equivalent
to restrictions in pipes
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Basic Electricity
Ohm’s Law and Joule’s law

Electrical energy is governed by Ohm’s Law and
Joule’s law

I = V/R (Ohm’s law)
 where I is Current (amps), V is voltage
(volts) and R is resistance (ohms).

P = V*I (Joule’s law)
 where P is Power (watts)

Electrical energy is expressed in watt hours
(power expended over a given amount of time)
Slide 16
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Basic Electricity
Ohm’s Law and Joule’s law
Example
 Circuit must be complete
for current to flow, if
switch is open nothing
happens.
 Current (I) = 12/3= 4
amps
 Power = 12 x 4 = 48 watts
 Energy over an hour = 48
watt hours
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Basic Electricity
Ohm’s Law and Joule’s law

The lamp will light 1
second after
throwing the switch!
Slide 18
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Basic Electricity
Ohm’s Law and Joule’s law

Now we can use these two formulae to show that :
 P = V2/R


In other words power is proportional to the square of
the voltage.
We can theoretically transfer four times the power if
we double the voltage (important concept)
Slide 19
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Basic Electricity
Electrical Losses and Parallel Paths
Slide 20
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Basic Electricity
Electrical Losses and Parallel Paths

Power losses occur when current flows though a resistance

P = V x I (Joule’s Law)

But V = I x R (Ohm’s Law)

Therefore P = I2 x R or I2R

These losses appear as heat – example is the electric kettle

In a transmission line the resistance of the line causes losses based
on this formula, the higher the resistance and the current the greater
the power losses.
Slide 21
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Basic Electricity
Series Path

Total Resistance R = R1 + R2 = 11 ohms

Therefore I = V/R = 100/11 = 9.09 amps

Line Losses = I2 R1 = 82.6 x 1 = 82.6 watts
R1 = 1 Ohm
Transmission
Line
V = 100 Volts
I = 9.09
amps
R2 = 10 Ohms
Load
(Customer)
Slide 22
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Basic Electricity
Parallel Path

I/R1 = 1/RA +1/RB + 1/RC = 1/1 +1/1 +1/1 = 3/1

Therefore R1 = 1/3 ohm = 0.333 ohms

Therefore total Resistance = R1 + R2 = 10.333 ohms

Therefore I = V/R = 100/10.33 = 9.7 amps and line losses = I2 * R1 = 31 watts
RA = 1 Ohm
R1
RB = 1 ohm
RC = 1 ohm
V = 100 Volts
Lines
I =9.7
amps
Load
(Customer)
R2 = 10 ohms
Slide 23
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Basic Electricity
Calculation: electrical voltage, current,
resistance, and power
Slide 24
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Basic Electricity
Alternating Current and Direct
Current
Slide 25
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Basic Electricity
Alternating Current and Direct Current
 DC stands for "Direct Current," meaning voltage or current that
maintains constant polarity and direction over time.
 AC stands for "Alternating Current," meaning voltage or
current that changes polarity and direction over time.
Slide 26
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Basic Electricity
Alternating Current and Direct Current
Slide 27
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Basic Electricity
Alternating Current and Direct Current
Slide 28
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Basic Electricity
Alternating Current and Direct Current
Slide 29
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Basic Electricity
Why Alternating Current (AC) is used and not Direct
Current (DC)




The transformer's ability to step AC voltage up or down with ease
gives AC an advantage unmatched by DC.
When transmitting electrical power over long distances, it is far
more efficient to do so with stepped-up voltages and stepped-down
currents, then step the voltage back down and the current back up
for industry, business, or consumer use.
Cannot run induction motors with DC, most industrial motors are
induction motors (simple and versatile).
DC is used to transmit power over very long distances but it is then
converted back to AC for end use
Slide 30
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Basic Electricity
How AC Power is Produced
Magnetism and Electricity are completely
intertwined
 Electric current (moving electric charge) creates
magnetism (discovered by Andre-Marie Ampere in
the 1820’s)
 Moving magnets create current in nearby
conductors (discovered by Michael Faraday also in
the 1820’s)
Slide 31
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Basic Electricity
How AC Power is Produced
Magnetism and Electricity are completely intertwined
 If the magnet does not
move there is no
attraction
 If the material is not a
conductor there is no
attraction
Slide 32
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How AC Power is Produced
When the magnet is
moved a current is
induced in the coiled
wire.
Magnet
Slide 33
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Basic Electricity
How AC Power is Produced
Slide 34
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Basic Electricity
How AC Power is Produced
 Magnetic lines of force are
stronger (more numerous) at
the two poles of the magnet
 When a rotating magnet
passes a stationary conductor
(wire) the induced current in
the wire is greatest when each
of the poles pass.
N
S
 This is why we get a sine
wave
Slide 35
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How AC Power is Produced
 The rotor of an AC
generator is a rotating
magnet(s).
 The stator of an AC
generator is a series of
stationary windings and
electric current is
induced in them by the
rotating magnet(s)
Slide 36
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Basic Electricity
How AC Power is Produced
Slide 37
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Basic Electricity
How AC Power is Produced
A rotor and stator for a
hydro-electric
generator (note the
number of poles)
Slide 38
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Basic Electricity
Frequency
Slide 39
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Basic Electricity
Frequency
 Measured in cycles per
second or Hertz.
 60 Hertz in North
America
 50 Hertz in Europe
 Time for 1 cycle = 1/60
= 16.66 milli secs
Slide 40
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Frequency
At what rotational speed must an AC generator spin at to
produce a frequency of 60 Hz?
 RPM = frequency x 120 divided by number of pole pairs, where
 RPM = revolutions per minute
 f = frequency in hertz
 Therefore the rotor of a machine with two pole pairs (typical fossil
fired unit) rotates at 3600 RPM
 Hydroelectric units rotate at much slower speeds, they have more
pole pairs.
Slide 41
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Basic Electricity
Frequency
 Frequency is the basic metric used to ensure that there is
sufficient generation to meet customer demand.
 Lower frequency (< 60 Hz) means customer demand not being
fully met
 Higher frequency (> 60 Hz) means that customer demand is being
oversupplied
Slide 42
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Basic Electricity
The Transformer
Slide 43
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Basic Electricity
The Transformer
Np x Ip = Ns x Is
Vp/Np = Vs/Ns
Slide 44
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Basic Electricity
The Transformer
Slide 45
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Basic Electricity
The Transformer
Slide 46
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Basic Electricity
Real and Reactive Power
 The concepts of
 Watts (real power)
 Volt ampere reactive, Var (reactive power or
imaginary power)
Slide 47
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Basic Electricity
Real and Reactive Power
 Reactive power is a concept used to describe the loss of power in a
system arising from the production of electric and magnetic fields.

Although reactive loads such as inductors and capacitors dissipate
no power, they drop voltage and draw current, which creates the
impression that they actually do.
 This “imaginary power” or “phantom power” is called reactive power.
It is measured in a unit called Volt-Amps-Reactive (VAR).
 The actual amount of power being used, or dissipated, is called true
power, and is measured in the unit of watts.
 The combination of reactive power and true power is called apparent
power, and it is the product of a circuit's voltage and current.
Apparent power is measured in the unit of Volt-Amps (VA).
Slide 48
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Basic Electricity
Real and Reactive Power
V=
 Power in a purely
resistive AC circuit
 All the power is
positive
Slide 49
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Basic Electricity
Real and Reactive Power
V=


Power in a purely
inductive AC circuit
Note that the power
is pulsating, no
power is absorbed by
the load.
Slide 50
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Real and Reactive Power
V=
 Power in an inductive
and resistive AC
circuit
 Note that although
most of the power is
positive, there is a
small pulsating
component
Slide 51
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Basic Electricity
Real and Reactive Power
 In a purely resistive circuit, all circuit power is dissipated by
the resistor(s). Voltage and current are in phase with each
other.
 In a purely reactive circuit, no circuit power is dissipated by the
load(s). Rather, power is alternately absorbed from and
returned to the AC source. Voltage and current are 90o out of
phase with each other.
 In a circuit consisting of resistance and reactance mixed, there
will be more power dissipated by the load(s) than returned, but
some power will definitely be dissipated and some will merely
be absorbed and returned. Voltage and current in such a circuit
will be out of phase by a value somewhere between 0o and 90o.
Slide 52
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Reactive Power
 Power provided and maintained for the explicit purpose of ensuring
continuous, steady voltage on transmission networks.

Reactive power must be produced for maintenance of the system and
is not produced for end-use consumption.
 Electric motors, electromagnetic generators and alternators used for
creating alternating current are all components of the energy delivery
chain which require reactive power.
 Losses incurred in transmission from heat and electromagnetic
emissions are included in total reactive power.
 This power is supplied for many purposes by generators, condensers,
capacitors and similar devices which can react to changes in current
flow by releasing energy to normalize this flow.
Slide 53
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Basic Electricity
Reactive Power
Why do we need Reactive Power?


To Maintain and Control the voltage balance on the power
system
To avoid damage to the
 Transmission system
 Generation plant
 Other connected parties
The provision of Reactive Power by all generating units for
voltage support is vital in maintaining a secure and stable
Transmission System
Slide 54
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Basic Electricity
Reactive Power – an analogy (sort of!)
 Consider walking across a trampoline.
 There is an up and down motion required to
traverse the trampoline.
 This up and down motion is analgous to reactive
power (required but not useful work)
Slide 55
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Impedance
 R = Resistance (ohms)
 XL = Inductive Reactance (ohms)
 XC = Capacitive Reactance (ohms)
 X = XL - XC (ohms)
Ohm’s Law still applies only
now it’s
I = V/Z
Slide 56
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Basic Electricity
Real and Reactive Power




Power dissipated by a load is referred to as true power. True power is
symbolized by the letter P and is measured in the unit of Watts (W).
Power merely absorbed and returned in load due to its reactive properties
is referred to as reactive power. Reactive power is symbolized by the
letter Q and is measured in the unit of Volt-Amps-Reactive (VAR).
Total power in an AC circuit, both dissipated and absorbed/returned is
referred to as apparent power. Apparent power is symbolized by the letter
S and is measured in the unit of Volt-Amps (VA).
These three types of power are trigonometrically related to one another. In
a right triangle, P = adjacent length, Q = opposite length, and S =
hypotenuse length. The opposite angle is equal to the circuit's impedance
(Z) phase angle
Slide 57
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Basic Electricity
Real and Reactive Power
Slide 58
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Basic Electricity
Real and Reactive Power
True, Reactive, and
Apparent power
Good paper on Reactive Power Supply can be found at:
http://www.ferc.gov/EventCalendar/Files/20050310144430-02-04-05-reactive-power.pdf
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Basic Electricity
Good explanations of reactive power
requirements in a power system
http://www.ferc.gov/EventCalendar/Files/20050310144430-02-0405-reactive-power.pdf
http://www.ornl.gov/sci/btc/apps/Restructuring/con453.pdf
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Power Factor
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Basic Electricity
Power Factor
 When expressed as a fraction, the ratio between true power
and apparent power is called the power factor.
 Because true power and apparent power form the adjacent and
hypotenuse sides of a right angle triangle, respectively, the
power factor ratio is also equal to the cosine of that phase
angle
 If the cosine of the angle is 0.9 then the angle is ~ 25 degrees
Slide 62
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Basic Electricity
Power Factor

For the purely resistive circuit, the power factor is 1 (perfect), because the
reactive power equals zero. Here, the power triangle would look like a
horizontal line, because the opposite (reactive power) side would have
zero length.

For the purely inductive circuit, the power factor is zero, because true
power equals zero. Here, the power triangle would look like a vertical line,
because the adjacent (true power) side would have zero length.

The same could be said for a purely capacitive circuit. If there are no
dissipative (resistive) components in the circuit, then the true power must
be equal to zero, making any power in the circuit purely reactive. The
power triangle for a purely capacitive circuit would again be a vertical line
(pointing down instead of up as it was for the purely inductive circuit).
Slide 63
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Basic Electricity
 Customer loads are generally a combination of resistive and
inductive, hence the aggregate load on the power system is
net inductive, ie customer loads absorb VARs.
 At off peak times lightly loaded transmission lines can have
a large capacitive effect.
 Hence during on peak periods generators have to produce
VARs and at off peak times have to absorb VARs
 Generators are required to be able to provide full Mw output
at 0.9 power factor lagging and 0.95 power factor leading
Slide 64
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Basic Electricity
Three Phase Power
Slide 65
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Three Phase Power
Single phase versus three
phase generator
 Could be any number of
phases but standardized at
three phase
 Can be compared to the
number of cylinders in your
car
 Industry uses all three
phases, households
normally only one.
Slide 66
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Basic Electricity
Three Phase Power
Each phase is 1200 apart
Slide 67
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Three phase power



All transmission lines are three phase
Some distribution lines (very low voltage) are
single phase
Loads on each phase normally balanced
Slide 68
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Basic Electricity
 Double circuit transmission
line
 Each line has 3 phases
 Phase Voltage is Phase to
Phase
 Line Voltage is Line to
ground
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Perspectives
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Basic Electricity
 Typical household load is about 10 to
20 kw
 And about 10 Mwh per year
 Total Ontario electrical energy in the
year ~ 150,000,000 Mwh or 150 Twh
Slide 71
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Basic Electricity
Some every day examples of power

Desktop Computer
80 w

One sq meter solar panel
120 w

Human brain
30 w

Electric kettle
1 Kw

A 200 horsepower car
150 Kw

Av electric power useage/capita in world
(in USA 12 Kw)
2.2 Kw

Diesel locomotive
3 Mw

Aircraft carrier
190 Mw

Three Gorges power station (China)
18 Gw

Peak load in Ontario
26.5 Gw

Hurricane
50 to 200 Tw
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The End
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